Biomedical Engineering Reference
In-Depth Information
These structures contain nickel particles on their tips, so that can penetrate cells
through a nanotube spearing procedure (Cai et al. 2005 ). When these nanotubes were
complexed with pDNA encoding EGFP, the nanotube spearing pathway resulted in
high transfection efficiency, particularly in nondividing neuron cells.
In addition to DNA transfection, CNTs have also been used to deliver siRNA
into cells for gene knockdown. Dai et al. noncovalently functionalized CNTs with
phospholipid-PEG moieties containing either maleimide or amine terminal groups
(Kam et al. 2005 ). These surface modified CNTs were reacted with thiol-terminated
siRNA and yielded nanoplexes. The nanoplexes thus obtained could inhibit the
gene encoding lamin A/C protein in HeLa cells. The same nanostructures also led
to an efficient delivery of siRNA into human T-cells and primary cells (Liu et al.
2007b ). Another example of gene knockdown using CNTs was reported by Zolk
and coworkers (Krajcik et al. 2008 ). Oxidized CNTs were reacted with hexameth-
ylenediamine, and then functionalized with poly(diallyldimethylammonium) chlo-
ride (PDDA). It was found that these CNT-based nanoparticles can cause 80%
inhibition of the targeted genes, ERK1 and ERK2 in vitro , when complexed with
siRNA through electrostatic interactions.
5.4
Silica Nanoparticles
Organically modified silica materials are normally nanocomposites and have the
potential for providing unique combination of properties, which cannot be achieved
by other materials. These surface-modified silica nanoparticles have many advan-
tages as candidates for gene delivery. For instance, colloidal silica nanoparticles are
inert and exhibit high biocompatibility, they are stable with respect to physical
stresses comparing with liposomes (Sameti et al. 2003 ).
Silica nanoparticles can be prepared by suitable sol-gel processing routes
(Brinker and Scherer 1990 ). The silanol groups on the surface allow an easy func-
tionalization. One of the successful examples is modifying silica nanoparticles with
sodium chloride reported by Chen et al. ( 2003 ). These particles had diameters of
10-100 nm and showed a transfection efficiency of about 70% exceeded than previ-
ously reported for lipoplexes mediated transfection. Lin et al. reported the first use
of mesoporous silica nanoparticles for gene delivery (Radu et al. 2004 ). PAMAMs
were covalently bound to the surface of mesoporous silica nanoparticles to promote
electrostatic interactions with pDNA. These cationic mesoporous nanoplexes were
successfully introduced into neural glia cells, human cervical cancer cells, and
Chinese hamster ovarian (CHO) cells, and showed higher gene transfection effi-
ciency than commercial transfection agents, such as PolyFect, SuperFect, and
Metafectene. This high efficiency was attributed to the increased sedimentation. The
DNA-binding capacity of cationic silica nanoparticles was first studied by Lehr and
co-workers (Kneuer et al. 2000 ). N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane
and N-(6-aminohexyl)-3-aminopropyltrimethoxysilane were used to modify silica
nanoparticles in their study. These nanoparticles showed significant transfection
in Cos-1 cells, especially in the presence of serum and chloroquine, which was
Search WWH ::




Custom Search